This week Advocacy for Animals presents an article by Kara Rogers, Encyclopaedia Britannica’s senior life sciences editor, on butterflies and their sensitivity to changes in climate and other aspects of environmental quality. The story originally appeared on the Britannica Blog in May 2008.

This summer eight species of butterflies found in the United Kingdom are in desperate need of good flying weather. Last yearâ€™s unusually rainy summer grounded them, leading to less breeding and feeding and resulting this spring in the lowest numbers counted for these species since butterfly record-keeping began in the United Kingdom some 25 years ago. Scientists and conservationists fear that it could take many years for these butterflies to mount a comeback, assuming they can do so at all; they will need near perfect conditions, meaning warm, dry weather for an extended part of the summer season.

The characteristic cool, wet climate of the United Kingdom makes it somewhat fascinating that butterflies so sensitive to damp weather chose to settle down in the region in the first place. But butterflies have been steadily pushing their way into northern climates for decades, primarily because such northern regions are heating up and becoming amenable to butterfly habitation. Butterflies are also highly sensitive to changes in their environment. They are, in fact, so sensitive to climate change, pollution, and habitat degradation that they serve as valuable indicators of potentially harmful environmental shifts.

In the United Kingdom, changes in climate and the effects of these changes on a wide range of animal species can be predicted from variations in the presence or absence of certain butterflies. Species such as the heath butterfly and the comma, which are typically found in warm areas and both of which have existed in England and in the southern parts of the United Kingdom for many years, have been gradually moving north into Scotland. They also have been emerging earlier in the year and sometimes producing multiple generations of offspring in one season.

The northern migration of these species has been linked with increases in temperature and with unusually dry weather in Scotland. While these species are busy carving out their niches in their new country, other species that are adapted to and that have survived in their damp, cool Scottish habitats for countless generations are in decline. For example, the range of the mountain ringlet, a rare species found only in the Scottish Highlands and in the Lake District National Park in England, has decreased, and its numbers are in decline. The loss of butterflies native to Scotland and of butterflies adapted to highly specialized habitats is due in part to climate change, but it is also the result of human activity.

Butterflies share unique relationships with the plants and animals around them. Caterpillars eat mainly leaves, and each species tends to feed on only one type of plant. If this plant is lost through habitat destruction or a change in climate, it can spell disaster for the survival of the butterfly species that is dependent upon the plant. Butterflies are important pollinators, although they are less efficient pollinators than honeybees. They also fill a vital role in the food web by serving as a food source for birds, lizards, snakes, and other predators.

Butterflies, as with many other insects, provide an initial and easy-to-miss glimpse into the impacts of climate change. These creatures are excellent environmental indicators because they catch our attentionâ€”they are beautiful and fragile and are a sign of life reemerging after a long winter. The chaos theory known as the butterfly effect is based on the idea that an initial change to a system sets in motion a chain of events that lead to a large-scale event. Could the realization that climate change can be evidenced by the presence or absence of butterflies be the initial step of a butterfly climate effect?

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